1. Field of the Invention
The present invention relates to a stamp apparatus and, in particular, to an apparatus for impressing a paper-sheet object with a mark continuously from a predetermined position to another predetermined position. The present invention is applicable, for example, to a machine for canceling a stamp bonded on a postal matter with a postmark (automatic flat canceling machine).
2. Description of the Related Art
A conventional stamp apparatus will be described with reference to FIG. 1. The stamp apparatus comprises a presser roller 31, an impress hub 32, a timing disk 33, a proximity switch 34, and a pair of photoelectric sensors 35a and 35b. 
The structure of the stamp apparatus will be described in detail. The presser roller 31, rotatably supported to one end of an L-shaped arm 36, is always rotated clockwise by a motor (not shown). The arm 36 is rotatable about a point of support 36a thereof. The other end of the arm 36 is pulled by a coil spring 37. Therefore, the arm 36 rotates counterclockwise, however, more than a predetermined rotational angle in the left direction is limited by a stopper 38. Adjusting the position of the stopper 38 changes the rotational angle of the arm 36 until a vicinity of the other end of the arm 36 abuts the stopper 38. As a result, a clearance (slightly smaller than the thickness of a paper-sheet object 30) is changed between the presser roller 31 and a part of printing types 32b (part having a predetermined character/symbol string) of the impress hub 32.
The impress hub 32 can counterclockwise rotate about the center 32a, and has the part of printing types 32b with a sectorial shape ranging over approximately 180xc2x0. The radius of the part of printing types 32b is larger than that of the impress hub 32. The sectorial timing disk 33 fixed to the impress hub 32 has a cut-out 33a ranging over approximately 90xc2x0.
At a predetermined time after an edge of a paper-sheet object 30 being conveyed at a predetermined speed passes through between an emitting sensor 35a and a receiving sensor 35b, the paper-sheet object 30 enters between the presser roller 31 and the impress hub 32, which are located at an initial position (position shown in FIG. 1). Then, since the presser roller 31 is pushed up by the paper-sheet object 30, the arm 36 rotates clockwise about a supporting point 36a. An impress-starting position on the paper-sheet object 30 reaches between the presser roller 31 and the impress hub 32, a motor (not shown) for the impress hub 32 rotates owing to the detection of the paper-sheet object 30 by the pair of sensors 35a and 35b and to a function of a delay circuit. Therefore, the impress hub 32 is rotated so as to initiate to impress the paper-sheet object 30 with the part of printing types 32b. When the impress hub 32 is rotated around in a complete circle and the cut-out 33a of the timing disk 33 is detected by the proximity switch 34, the impress hub 32 stops at the initial position. Up to this point, one cycle of impress is completed.
As the surface of the presser roller 31 is made of an elastic material such as rubber, the surface is slightly compressed when being urged by the paper-sheet object 30.
In the conventional stamp apparatus, the urging force of the presser roller 31 to the paper-sheet object 30 is adjusted with the coil spring 37. Therefore, a paper-sheet object 30 having a predetermined thickness or more cannot pass through between the presser roller 31 and the part of printing types 32b of the impress hub 32.
It is an object of the present invention to provide a stamp apparatus, in which even a thick paper-sheet object can pass through between a presser roller and a part of printing types of an impress hub.
According to the present invention, a stamp apparatus is provided, which comprises an impress hub having a predetermined character/symbol string, a presser roller for urging a paper-sheet object to the impress hub, for impressing the predetermined character/symbol string to the paper-sheet object being conveyed between the impress hub and the presser roller, and a presser mechanism, comprising an arm having the presser roller, for suppressing a rebound produced when the presser roller starts to urge the paper-sheet object by rotating the arm so as to urge the presser roller to the paper-sheet object and simultaneously for maintaining a predetermined urging pressure of the presser roller relative to the paper-sheet object having a predetermined thickness at most.
The present invention described above has advantages as follows.
1. A thick paper-sheet object having a predetermined thickness and below can smoothly pass through between the presser roller and the impress hub.
2. A rebound produced when the presser roller starts to urge a paper-sheet object to the impress hub is suppressed so that the paper-sheet object having a predetermined thickness and below can be clearly impressed.
3. As the stamp apparatus may further comprise a separating lever, the separating lever separates a paper-sheet object from the impress hub immediately after completion of impressing the paper-sheet object by the impress hub, so that the needless contact between the paper-sheet object and the impress hub can be avoided.